JP6307161B2 - Auxiliary heating in waste heat recovery - Google Patents

Description

  The present invention relates to bottoming cycle devices, such as Rankine cycle devices, for recovering energy from waste heat of internal combustion engines, and more particularly to ensuring that the working fluid is at a temperature sufficient for the operation of the waste heat expander. The present invention relates to a method and an apparatus.

  In bottoming cycle devices, such as devices based on Rankine cycles, system efficiency is directly related to the uptime, i.e. the operating time during which waste heat recovery occurs. Non-operational periods are often caused by low quality heat (not enough waste heat) and part preheating time (when warming boilers and expanders) that are available. For example, a waste heat recovery device connected to a truck engine may not be operating immediately after starting and warming up the engine.

  The present invention proposes a solution to increase the operating time by improving the temperature management during low quality heat availability and to reduce the preheating time of the device when returning to operation.

  The present invention can be applied to bottoming cycles such as Rankine cycle, Ericsson cycle and other waste heat recovery cycles.

  The bottoming cycle apparatus can include an expander connected to a working fluid circuit for receiving a working fluid from a waste heat recovery heat exchanger, such as a boiler, an evaporator, or a heat exchanger. The working fluid guided to the expander expands in the expander to generate usable work or energy.

  In accordance with the present invention, a heating device operably connected on the working fluid circuit is not sufficient for the waste heat recovered by the waste heat recovery heat exchanger to increase the working fluid enthalpy to the expander operating level. In some cases, it provides auxiliary heat to the working fluid.

  The heating device can include a burner or an electrical heating device disposed with the heat exchanger to heat the working fluid. The burner can include a fuel source, for example, a hydrocarbon fuel such as diesel. The electrical heating device can be connected to receive electrical energy from a source such as a vehicle power supply system.

  The control device can be connected to control the operation of the heating device and to monitor the temperature and pressure of the working fluid (measurable at the boiler outlet).

  The heating device can be placed on the working fluid circuit between the boiler and the expander. Alternatively, the heating device can be placed on the working fluid circuit between the pump and the boiler.

  According to yet another alternative, the heating device can be placed on the boiler to add heat to the waste heat source stream. For example, if the boiler is connected to receive a flow of engine exhaust gas as a waste heat source, the auxiliary heating device can be arranged to add heat to the exhaust gas as it enters the boiler.

  According to the present invention, the working fluid circuit may include a heating loop in which an auxiliary heating device is arranged, the heating loop being controlled by a valve, which enters the expander depending on the thermal quality of the working fluid. The working fluid is guided directly to the expander or heating loop before it is done.

  According to yet another aspect, the working fluid circuit may include a bypass circuit around which the working fluid is guided when the thermal quality is low or when the operation of the expander is undesirable.

  According to one embodiment, the bypass circuit includes a first loop in which an auxiliary heating device is disposed and returns the working fluid to the expander, i.e., a heating loop, and the first loop to bypass the expander. And a second loop for guiding.

1 is a schematic view of a typical Rankine cycle device according to the prior art. It is the schematic of the Rankine cycle apparatus which has a bypass circuit for making a working fluid bypass an expander. 1 is a schematic diagram of a bottoming cycle device according to one embodiment of the present invention, in which an auxiliary heating device is provided to selectively add heat to a working fluid. FIG. FIG. 4 is a schematic diagram of an alternative embodiment of the apparatus of FIG. 3 including a bypass circuit around the expander. FIG. 4 is a schematic diagram of another alternative embodiment of the apparatus of FIG. 3 including a first bypass circuit provided with an auxiliary heating device and a second bypass circuit around the expander. FIG. 2 is a schematic view of a bottoming cycle device according to an alternative embodiment, in which a heating device is provided upstream of the boiler. FIG. 6 is a schematic diagram of a bottoming cycle device according to a further alternative embodiment, in which a heating device is provided at the waste heat inlet to the boiler.

  As shown in FIG. 1, a typical bottoming cycle waste heat recovery system includes a heat source (not shown), eg, waste heat from an internal combustion engine exhaust, engine coolant, engine oil cooler for heating a working fluid. Or an evaporator or boiler 10 for recovering heat from other sources. The inflow pipe 11 at the boiler inlet conducts a waste heat transport medium (for example, exhaust gas) to the boiler 10, and the outflow pipe 13 transports the medium exiting from the boiler outlet after heat exchange. The working fluid is transported through the waste heat recovery device by the working fluid circuit 12. The heated working fluid leaving the boiler 10 is guided to the expander 14 through the working fluid circuit line 12a where it generates work by expanding the working fluid. The expander may be a turbine, piston engine, scroll, screw, or other machine. The generated work can be transmitted through the shaft 15 and can be used, for example, to drive the generator, i.e. as mechanical force applied to the drive shaft of the internal combustion engine. The expanded working fluid is guided to the condenser 16 through the circuit line 12b, where residual heat is removed from the working fluid and the working fluid is condensed. The condensed fluid is then guided to pump 18 through circuit line 12c where it compresses the working fluid. The circuit line 12c transports the working fluid from the pump 18 to the boiler 10 and repeats the waste heat recovery cycle.

  As shown in FIG. 2 and as is well known in the art, the bottoming cycle waste heat device includes a bypass valve 20 and a bypass circuit 22 for selectively guiding the working fluid around the expander 14 to the condenser 16. Can be included. The bypass valve 20 guides the expander 14 through line 24 when the working fluid is in operation, or through line 22 if power generation by the expander is not desired or the quality of the working fluid is not sufficient for expansion. Control can be performed to bypass the expander 14. For example, if there is not enough waste heat available in the boiler 10 to heat the working fluid to the operating temperature, such as superheated steam, the quality of the working fluid may not be sufficient. The condenser 16 cools the working fluid received from the bypass circuit, and the cooled fluid is pumped to the evaporator / boiler 10 by a pump 18.

  FIG. 3 illustrates one embodiment of an apparatus according to the present invention. The apparatus of FIG. 3 includes a heating device 40 operably connected to the working fluid circuit 12 to provide supplemental heat to the working fluid. The heating device 40 is shown connected between the evaporator 10 and the expander 14. If the heat recovered by the evaporator 10 and transferred to the working fluid is not sufficient for use in the expander 14, the heating device 40 can be operated to add auxiliary heat to the working fluid.

  The heating device 40 can be configured as a heat exchanger with heat supplied by a burner or an electric heating device.

  The heating device 40 is connected to receive energy from the energy source 44. The heating device 40 may be a burner device and the energy source 44 may be a hydrocarbon fuel. The fuel may conveniently be the same fuel used by the engine that generates waste heat. The heating device 40 may instead be an electric heater or an energy source configured as an electric energy source. For example, if the waste heat recovery device is associated with a truck, the truck's electrical system can be connected as an energy source. Other heating devices may be used.

  The heating device 40 can operate based on the detected temperature of the working fluid exiting the boiler 10. A temperature sensor 46 on the working fluid circuit 12 a at the outlet of the boiler 10 or on the outlet side of the boiler can be connected to provide a temperature signal to the controller 48, which is connected to the sensor 48 from the sensor 46. It connects so that the heating apparatus 40 and the energy source 44 may be controlled according to a temperature signal.

  The heating device 40 can also be controlled based on other operating conditions such as the pressure of the working fluid. In addition, a temperature sensor 62 on the outlet side of the expander (or condenser inlet) can monitor the temperature of the expanded working fluid exiting and provide a signal to the controller 48.

  FIG. 4 is a schematic diagram of an alternative embodiment of the apparatus of FIG. The bypass valve 20 is provided to guide the working fluid to bypass the expander 14 through the bypass circuit 22 if the thermal quality is not sufficient for expansion. Bypass valve 20 may remove the working fluid from expander 14 if the thermal quality of the working fluid is not sufficient for expansion, from waste heat recovered from boiler 10, from auxiliary heat from heating device 40, or both. Is controlled to guide. The bypass valve 20 is controlled by a control device 48 according to conditions including the temperature of the working fluid measured by the sensor 46 on the outlet side of the boiler and / or the sensor 47 on the outlet side of the heating device 40.

  FIG. 5 shows that when the heat quality of the working fluid flowing from the boiler 10 is sufficient, or when auxiliary heating is required, the first bypass valve 20a is provided in the first bypass circuit 22a in which the auxiliary heating device 40 is disposed. Figure 2 shows another alternative embodiment including: The second bypass valve 20b is downstream of the heating device 40 and guides the working fluid through the circuit 22b to the expander 14 when the thermal quality of the working fluid is sufficient for expansion, thereby terminating the first bypass circuit. To do. The second bypass valve 20b guides the working fluid through the second bypass circuit 22c when the thermal quality of the working fluid is not sufficient for expansion. The first bypass valve 20a and the second bypass valve 20b are controlled according to operating conditions including the temperature of the working fluid measured by the sensor 46 on the outlet side of the boiler 10 and the sensor 47 on the outlet side of the heating device 40. It is controlled by the device 48.

  According to an alternative embodiment of FIG. 5, the second bypass valve 20b and the second bypass circuit 22c are omitted, and the first bypass valve 20a, the bypass circuit 22a and the heating device 40 constitute a heating loop. . The bypass valve 20a is controlled to guide the working fluid directly to the expander or heating loop for auxiliary heating before the working fluid is guided to the expander.

  FIG. 6 is a schematic diagram of an alternative embodiment. The heating device 40 can be connected between the pump 18 and the boiler 10 to the working fluid circuit 12 on the inlet side of the boiler 10. The bypass valve 20 and the bypass circuit 22 can also be provided to guide the working fluid to bypass the expander when operation of the expander is not desired or when the quality of the working fluid is not sufficient for expansion.

  FIG. 7 is a schematic diagram of another alternative embodiment in which the heating device 40 is connected on the waste heat inlet pipe 11 of the boiler 10. The bypass valve 20 and the bypass circuit 22 can be provided similarly to the other embodiments.

  The invention has been described with reference to preferred principles, embodiments and components. Those skilled in the art will appreciate that component substitutions can be made without departing from the scope of the invention as defined by the claims.

Claims (9)

In a vehicle waste heat recovery apparatus having an internal combustion engine with an exhaust gas system
A working fluid circuit for circulating the working fluid;
A boiler connected on the working fluid circuit and configured to recover waste heat from the exhaust gas system and to transfer the recovered waste heat to the working fluid;
An expander connected on the working fluid circuit to receive the working fluid from the boiler;
An auxiliary heating device including a burner or an electric heater connected to transfer heat to the working fluid ;
A temperature sensor arranged to detect the temperature of the working fluid at the outlet of the boiler and generate a temperature signal representative thereof;
The working fluid is connected to receive the temperature signal from the temperature sensor and heats the working fluid in response to the temperature signal indicating a temperature of the working fluid flowing out of the boiler that is not sufficient for an operating level of the expander. And a controller connected to control the auxiliary heating device to communicate
Waste heat recovery equipment for vehicles . The waste heat recovery apparatus for a vehicle according to claim 1, wherein the auxiliary heating device is connected to the working fluid circuit between the boiler and the expander. The waste heat recovery apparatus for a vehicle according to claim 1, wherein the auxiliary heating device is connected to the working fluid circuit between the pump and the boiler. The waste heat recovery apparatus for a vehicle according to claim 1, wherein the auxiliary heating device is connected to transmit heat to the boiler. The vehicle waste heat recovery apparatus according to claim 1, further comprising a bypass valve and a bypass circuit connected on the working fluid circuit to selectively guide the working fluid to bypass the expander. The waste heat recovery device for a vehicle according to claim 5 , wherein the auxiliary heating device is connected to the working fluid circuit between the boiler and the bypass valve. A second bypass valve, wherein the bypass circuit guides the working fluid to the second bypass valve by the first bypass valve and then to the expander by the second bypass valve. A circuit and a second bypass circuit in which working fluid is guided by the first bypass valve to the second bypass valve and then by the second bypass valve to bypass the expander. Item 6. A waste heat recovery apparatus for a vehicle according to Item 5 . The auxiliary heating device is arranged in the first circuit on a vehicle for waste heat recovery apparatus according to claim 7. Comprising a valve connected on the working fluid circuit to selectively guide working fluid to one of the expander or heating loop, and the auxiliary heating device is disposed on the heating loop; The waste heat recovery apparatus for vehicles according to claim 1.

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